Citric acid and sodium citrate are commonly used bathroom cleaners. Many cleaning compositions use citric acid, below a pH of 3, in order to achieve cleaning performance on various hard surfaces. In addition, sodium citrate is commonly used at a pH near 7, however the neutral citrate salt does not provide as superior cleaning efficacy as that achieved by the acidic citric acid compositions. The increase in pH of the citrate salt decreases the cleaning power of the compositions, such that the majority of hard surface and/or bathroom cleaners employing citric acid and/or its salt prefer lower pH ranges, particularly pH less than 3. See e.g. U.S. Pat. Nos. 6,221,823, 6,936,579, 7,199,094, 7,696,143 and 8,268,334, which are herein incorporated by reference in their entirety.
Citric acid and/or compositions having a pH below about 3 are particularly well suited for cleaning soap scum, scale (i.e. hard water stains and lime scale as may also be used to refer to such stains commonly found in bathrooms) and/or other residues as is commonly found in bathrooms due to is triprotic acid strength when formulated at pH values less than about 3. The removal of soap scum and scale requires the strength of an acid to effectively clean due to the presence of calcium and magnesium salts and soap residues. Similarly, the acid component is needed to treat hard water stains, which are mineral stains caused by the deposition of salts, such as calcium or magnesium carbonates, frequently present in hard water. Still further, the strength of acidic products are further needed for removing soap scum stains, which include the residues of fatty acid soaps which are often based on alkaline salts of low fatty acids known to precipitate in hard water due to the presence of metal salts therein leaving an undesirable residue upon such surfaces.
It is known in the art that highly acidic cleaning agents such as strong acids effectively remove hard water stains. However, there are numerous toxicological concerns as well as environmental concerns associated with such cleaning compositions. Other compositions known to effectively remove soap scum use high concentrations of organic and/or inorganic acids along with detergents. However, these compositions may have limited efficacy against other types of stains often found on hard surfaces, namely in bathrooms, and further have toxicological concerns.
Accordingly, it is an objective of the claimed invention to develop improved cleaning compositions having milder pH ranges than citric acid compositions below pH 3 while providing at least substantially similar cleaning efficacy, if not greater efficacy, than unneutralized citric acid.
In particular, it is an objective of the claimed invention to provide improved bathroom and hard surface cleaners having Green Seal approval for use as environmentally-friendly cleaning compositions.
A further object of the invention is to create moderately acidic and/or alkaline bathroom and/or hard surface cleaners providing highly effective soil removal capabilities through the chelation mechanism of the partially neutralized citric acid salts.
A further object of the invention is to provide highly effective, safe to use, cleaning compositions employing partially neutralized citric acid salts.